SlateHouzz user Melissa Johnson says in this discussion on Houzz that she had slate floors in the kitchen and dining area that looked great but were a "disaster to clean" because of the stone's many nooks and uneven surfaces. For natural stone like slate, it's advisable to apply a penetrating sealer to countertops and slate floors every two years to prevent deep stains. Clean slate tiles with a few drops of dishwashing liquid and warm water applied to the slate surface with a soft cleaning tool, like a mop, sponge or soft cloth. For tough stains: Clean soap scum with a half-cup of ammonia per 1 gallon of water. Stay away from: Abrasive cleaners, vinegar and citrus cleaners.